Saturated steam at 100°C condenses outside a tube. Cold fluid enters the tube at 20°C and leaves at 50°C. Find the log mean temperature difference in °C.
Condensing steam remains at 100°C. The terminal differences are therefore $\Delta T_1=100-20=80$ K and $\Delta T_2=100-50=50$ K. The logarithmic mean is $(80-50)/\ln(80/50)=63.829$ K. A temperature difference has the same numerical value in K and °C, giving 63.83°C.
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